Measurement and Enhancement of Coalescence-Induced Droplet Jumping in the V-Shaped Superhydrophobic Trench with a Curved Ridge.

Abstract

Coalescence-induced droplet jumping demonstrates significant potential for diverse applications. However, current studies on enhancing and regulating droplet jumping largely focus on specific droplet locations and enhancement structures, significantly restricting their broader applications. This study introduces a V-shaped superhydrophobic trench with a curved ridge to enhance and control droplet coalescence jumping and directional transfer. Experimentally, a dimensionless jumping velocity (Vj* ≈ 0.69) and energy conversion efficiency (η ≈ 42.13%) were achieved, representing about 111.63% improvement in energy conversion efficiency compared to the V-shaped trench and an 879.77% increase relative to planar superhydrophobic surfaces, with a jumping angle of 66°. Numerical simulations and experiments revealed that the curved ridge enhances droplet coalescence jumping velocity and enables directional control by redirecting velocity vectors and minimizing viscous loss during coalescence. Additionally, the effects of ridge length, height, width, and opening angle on droplet coalescence jumping were analyzed via numerical simulations, offering theoretical support and technical guidance for practical applications. The coalescence jumping of droplets with unequal sizes on curved ridge structures was also studied, demonstrating that droplets with radius ratios below 0.66 can bounce off trench surfaces, confirming the structure's general applicability. This study further proposes a droplet velocity measurement method integrating target detection and trajectory fitting, achieving efficient and precise droplet velocity determination.